The invention relates generally to color-television picture tubes and in particular to an improved and novel picture tube wherein purity adjustment, vertical pincushion correction, and static convergence correction are performed by magnetic fields produced by permanent magnets acting on the beams.
Such adjusting and correcting devices provided with permanent magnets are slipped over the tube neck and locked there. They consist of rotatable pairs of magnetic rings, it being possible to change the field strength by rotating the rings of a pair against each other, and the field direction by rotating the pair. Such a device is described in a data sheet entitled "VALVO-Ablenkteile: Mehrpoleinheit DT 10 81", December 1973. The adjustment is effected by means of plastic gears and pinions, and since four pairs of magnetic rings have to be adjusted, a relatively expensive unit is obtained which is needed virtually only in the event of a tube change. Other prior art aspects of color-television picture tubes are shown in German prior art DT-OS No. 22 49 474 and DT-OS No. 24 08 994.